Theodosian is a data-centric security platform that applies encryption and dynamic access controls directly to files rather than relying on perimeter-based security. The platform operates on existing data storage infrastructure without requiring data migration. The solution implements zero-knowledge encryption using FIPS 140-3 standards, ensuring that encrypted data cannot be decrypted even if Theodosian itself is compromised. Files remain protected regardless of where they are created, stored, moved, or accessed, including when they leave corporate networks or cloud environments. The platform supports compliance requirements including CMMC, ITAR, HIPAA, and CJIS. It provides audit evidence generation and policy enforcement capabilities. Theodosian is designed to address security gaps that occur when valid credentials are compromised or insider threats emerge, scenarios where traditional perimeter controls fail. The solution integrates with existing file storage systems including SharePoint, Google Drive, Dropbox, and NFS. It offers flexible deployment options and self-custody key management. The platform is designed for organizations ranging from small businesses to enterprises and government agencies requiring FedRAMP compliance and zero-trust architecture support.